This invention relates to a method for determining a protein component in a fluid and/or determining the total protein concentration in the fluid.
In many situations, it is important to know both the concentration of a single marker protein, such as serum albumin, and the total protein concentration in a biological fluid, such as serum, urine, or cerebrospinal fluid. For example, human serum albumin is frequently assayed in biological samples for any one of a number of reasons. The concentration of this protein can be used to detect protein catabolism as the result of tissue damage or inflammation, the reduced absorption of amino acids caused by malabsorption syndromes or malnutrition, protein loss due to kidney disorders such as nephrotic syndrome or chronic glomuleronephritis, or other conditions affecting protein metabolism and balance. One condition in which human serum albumin occurs at low concentrations in urine is diabetes mellitus.
Other proteins found in serum, such as .alpha..sub.1 -antitrypsin, .alpha..sub.1 -acid glycoprotein, and C-reactive protein, are all markers of inflammation, particularly in the acute phase. Still other proteins, such as .alpha..sub.1 -fetoprotein and carcinoembryonic antigen, are also frequently monitored as potential markers of malignant disorder. Other proteins are frequently assayed as markers for particular disease states or inflammatory conditions.
Typically, quantitative protein determination of serum is done by nephelometric methods or colorimetric methods. Qualitative analysis of serum is typically done by gel electrophoresis in one or two dimensions. In a few cases of extremely abundant proteins, such as human serum albumin, dye binding methods are available, such as the determination of albumin with bromocresol green.
However, those methods that give qualitative separation and determinations of the proteins in a complex biological sample such as plasma, such as two-dimensional electrophoresis, cannot readily give accurate quantitative determinations of either the concentration of a particular protein of interest or of the total protein concentration in the sample. Similarly, methods that determine total protein concentration accurately cannot determine the concentration of particular proteins in the sample. Thus, multiple tests must be done to obtain both of these results. This requires additional instrumentation, more samples, and more time. It also increases the likelihood of error or contamination occurring in one of the tests.
Thus, there is a need for an improved method of protein determination that yields a qualitative analysis of the proteins in a sample and also yields the concentration of any particular protein in the sample as well as the total protein concentration. Preferably, such a method is suitable for the determination of a large number of proteins and can operate over a wide range of protein concentrations. Preferably, the method can handle a wide range of biological samples as well as non-biological samples, including urine, cerebral spinal fluid, tears, seminal fluid or vaginal fluid, and environmental waste samples.